First important Q: are you able to discuss this with a real MD? At 70+, there may be some considerations not relevant to an ED case in their 40s. Are you afraid that your personal physician might wonder why you want the meds or spill the beans to a family member?  Is there a Planned Parenthood or other clinic in your area? (Does PP help with ED at all?)  

A big caution about the "natural herbs" ED packets you see at the checkouts in gas stations and convenience stores: they are very often spiked with unlicensed versions of real drugs but in unknown amounts. Even if it was thought to contain sildenafil, you wouldn't know the dose in the packet.  

Be careful getting medical advice on the internet!

I recommend you get a prescription from your doctor for Sildenafil ( Viagra )  
( if Viagra is your choice ) I personally like Viagra cause I don't have to walk with a boner  
for next 36 hours ( Thanks Cialis

Anyway , I would ask your doctor for 90 pills ( 20mg Each )  
II have a plus membership at Sam's Club ,  there I buy 30 pills for  $10 !!!!  

Yes , $10 for 6 days worth of hard core cock !  

you cant beet that deal.  

you can take 1 to 5 pills at the same time.  
If you take 5 pills its like you took 100mg of Viagra .  
Works great for me.  

Cialis I like too but I noticed my erections don't get as hard as on Viagra  
and then I get none stop boner for next 36 hours .  
With Viagra , usually 3-4 hour and the pill starts to ware off